1. Field of the Invention
This invention relates to cutting machines and more particularly to a machine for opening the joints and random cracks in pavement preparatory to the insertion of a filler-sealant material therein.
2. Description of the Prior Art
Large expanses of concrete or asphalt paved surfaces such as roadways, airport runways, and the like, often develop random cracks during curing and after periods of extended usage. Such cracks should be sealed to prevent further spreading and the general deterioration of the paved surface, and to insure safe usage of the surface. In addition to sealing of random cracks, proper maintenance of paved surfaces is ideally accomplished by periodically replacing the sealing materials in expansion joints of the pavement. To prepare a paved surface for sealing of random cracks and resealing of expansion joints, the cracks and joints are opened and cleaned so that the filler-sealant, such as asphalt, can properly enter into and firmly adhere to the sides of the cracks and joints.
Several types of machines have been used to open and clean the cracks and joints in paved surfaces, and in general, these prior art machines are very slow and extremely difficult for an operator to manipulate and otherwise control.
A first general type of prior art machine includes a large flat carriage frame having wheels at each of the corners thereof. A suitable gas operated engine is mounted on the carriage and is coupled such as by a belt or chain, to drive a rotary cutter such as a cutter wheel or saw. The rotary cutter is carried in a suitable linkage which allows raising and lowering of the cutter. This type of machine is adequate for opening and cleaning of expansion joints in that such joints are in a straight line. When it comes to opening and cleaning random cracks, this type of machine is inadequate due to the lack of maneuverability which means that it is virtually impossible to follow a random path without producing excessive widening of the crack at each point where the path changes direction.
Another prior art machine, as shown in U.S. Pat. No. 3,663,060 includes a carriage having a rearwardly disposed oppositely mounted pair of wheels and a swivel wheel on the front of the carriage. A frame is pivotably mounted on the carriage for supporting an engine which drives a circular saw that is rotatably journaled on the frame and is laterally offset between the side rails of the carriage. The circular saw is disposed on the pivotable frame so that its axis of rotation lies between the rear wheels of the carriage, and pivotable movement of the frame will cause that axis of the circular saw to move in an arcuate path that passes through the axis of the rear wheels of the carriage. With regard to the maneuverability, this prior art machine is a substantial improvement. However, some problems still exist. The laterally offset disposition of the circular saw between the side rails of the carriage is not ideal in that the arcuate path, or turning radius, that the saw follows when the machine is turned in one direction is different from the path followed when the machine is turned in the opposite direction. Also, it is extremely difficult, if not impossible, to turn the machine about a stationary vertical axis that passes through the center of the circular saw due to the laterally offset disposition thereof which results in a tendency for the vertical axis to move as a result of the wheels revolving at different rates when the machine is trying to be turned about such an offset axis.
The above described prior art machines, and all others to the best of our knowledge, have other problems and shortcomings arising from the direction in which such machines are pushed or guided by the operator. An operator will stand behind the machine and push it along the path of the joint or crack. This means that it is physically impossible for the operator to see the crack or joint immediately in front of the cutting saw or wheel in that his view is obstructed for at least a foot or two in front of the cutting saw by the machine itself, and he must try to look through a cloud of dust and pavement chips which are being ejected forwardly of the machine. Another problem in these prior art machines, is that pushing of the machine as described above, will quickly tire an operator as such pushing motion must be accomplished against the tendency of the machine to propel itself rearwardly. Such a tendency results from the biting action and frictional engagement of the rotary cutter with the concrete, and the direction of this self-propelling tendency is dictated by the rotational direction of the rotary cutter which cannot be reversed in that the dust and pavement chips must be propelled away from the operator, i.e., forwardly of the machine.
Therefore, a need exists for a new and improved pavement cutting machine which overcomes some of the problems and shortcomings of the prior art.